The present invention relates to the use of the sex pheromone, E8,E10-dodecadien-1-ol, codlemone, in combination with one or two behavioural antagonists and/or behavioural synegists for control of codling moth, Cydia pomonella (Lepidoptera, Tortricidea) in fruit orchards by mating disruption or male attraction.
Biological methods of controlling pest insects have been faced with great interest during later years and in particular the use of pheromones, i.e. species specific scent substances which animals, such as insects, use to communicate and which substances elicit a certain behaviour or a biological activity. For several years pheromones have been marketed for control of certain pest insects on a commercial basis. The advantage of using pheromones for this purpose is the very high selectivity and the very great environmental advantage. Contrary to chemical inhibiting agents such as insecticides, the activity of the pheromones is directed solely towards the insect species intended, and as pheromones are substances that appear naturally, they do not give rise to resistance problems. Pheromones are active in very small amounts and are biologically degradable. They are not toxic to any part of the ecological system.
Sex pheromones of butterflies (in particular night moths and torthricides) are the most well known sex pheromones. In one control method, the confusion method, the pheromone is spread from sources provided with a synthetic sex pheromone substance in such a way that the whole area will become reeking with the substance. The males will then not find the females to any greater extent. The method is efficient. The confusion method is currently commercial with regard to a dozen moth species (Cardxc3xa9 and Minks, 1955, Ridgway et al, 1990). The most important obstacles for a rapid development of the confusion technique are within the fields of biology and chemistry. One does simply not know how and why the confusion technique works.
The dominant hypothesis for the male pheromone attraction of the females was formulated in 1978 by Roelofs. It is called the threshold hypothesis and states that the complete and proportionally natural pheromone blend is always a better stimulus of the complete behaviour than any other blend of the components. It will also release the behaviour at lower concentrations than any other blend. The hypothesis has governed and still governs, in principle, all pheromone studies.
In a review of successful and commercial cases using confusion, Minks and Cardxc3xa9 conclude (1988): xe2x80x9cthe natural blend achieves disruption of mating at lower application rates than either partial or off-ratio blendsxe2x80x9d.
A sex pheromone may consist of up to 10 different, but biosynthetically closely related substances (Baker, 1989). Different species within a family utilize different combinations of such a theme. The species separation can be strengthened by the fact that species A has specific sensory neurons for the main component of species B as well, but responds with a negative, escaping behaviour on such a signal. As an example, the pine sawflies (hymeropteran) of the family Diprionidae (Lxc3x6fqvist, 1986) will be mentioned. The main component of the sex pheromone of Neodiprion sertifer has three chiral carbon atoms. The substance can thus appear in eight different enantiomers. Only one of them is active as a sex attractant. Another one thereof is a very strong behaviour antagonist. Only 1-2% of this together with the attractant is enough to completely block the attraction.
The main component of the sex pheromone of the codling moth, E8,E10-dodecadien-1-ol was identified in 1971 by Roelofs et al. Several research groups then worked with the identification of the composition of the pheromone. A relatively complete composition was published by Einhorn et al (1984) and Arn et al (1985) Roelofs et al (1972) found that the EE-isomer of the geometric isomers was very attractive while the other three inhibited the attraction of the codling moth. The commercial product thus consequently consists of 99% EE-isomer.
Mating Disruption
Insects use sex pheromones to communicate for mating. Pheromones elicit strong behavioural reactions in minute amounts, they are species-specific and non-toxic. By permeating the atmosphere with synthetic pheromones, olfactory communication and mate-finding can be prevented.
The economic importance of pheromonal methods of insect control is increasing due to problems with registration of toxic insecticides, insect resistance, environmental problems and consumer attitudes. Among the advantages of using pheromones is their specificity, the fact that they are active in very low amounts, and that they are not known to be toxic to any part of the ecological system.
The mechanisms of mating disruption (confusion) are still largely unknown. Pheromones usually consist of a blend of several compounds, which are attractive to conspecific males, but unattractive or even repellent to males of other species (Cardxc3xa9 et al, 1977; Witzgall et al. 1996b). The addition of pheromone synergists and pheromone antagonists, i.e. positive and negative agonists enhance the male behavioural response.
Successful attempts to control moths (Lepidoptera) by mating disruption include both blends of the main pheromone compounds and pheromone antagonists, as well as blends of pheromone and pheromone synergists (Minks and Cardxc3xa9 1988; Bengtsson et al. 1994). However, there are no known cases where the main compound alone has shown to be more efficient than blends of the main pheromone compound with synergists or antagonists.
Male Annihilation
Male attraction to point sources of pheromone is also used to control insects. These pheromone sources can be used in large-capacity traps, or can be formulated together with insecticides (xe2x80x9cattract and killxe2x80x9d; Charmillot and Hofer 1997).
A more complete synthetic pheromone blend is more attractive and thus more efficient than less complete blends. With the attract and kill method, it is important to attract the males close enough to the poisoned bait to ensure contact. We have shown that more complete pheromone blends which come as close as possible to the calling female, are more efficient.
It is possible to control the codling moth, Cydia pomonella, by confusion using the sex pheromone E8,E10-dodecadien-1-ol in a combination with one or more behaviour antagonists (EP-A-0 820 226, WO96/27289). Suitable behaviour antagonists are one or more of the geometric isomers of delta8,delta10-dodecadien-1-yl acetate. Further, the codling moth can be attracted and killed using a behavioural synergist using one or more of the substances of the group Z8-dodecen-1-yl acetate, E8-dodecen-1-yl acetate, Z10-dodecen-1-yl acetate and E10dodecen-1-yl acetate, or a very small amount of the geometric isomer E8,E10-dodecadien-1-yl acetate, which is synergistic.
The present invention provides an efficient method for controlling codling moths, Cydia pomonella, in fruit orchards by mating disruption or by attraction and killing, comprising the step of exposing the moths to E8,E10-dodecadien-1-ol in combination with one or more behavioral antagonists or behavioral synergists. Suitable behavioral antagonists include the geometric isomers of delta 8, delta 10-dodecadien-1-yl acetate. Suitable behavioral synergists include Z8-dodecen-1-yl acetate, E8-dodecen-1-yl acetate, Z10-dodecen-1-yl acetate and E10-dodecen-1-yl acetate, as well as a very small amount of the geometric isomer E8,E10-dodecadien-1-yl acetate, which is synergistic.